Electrical Tips: Replacing a Light Fixture

Replace a light fixture more quickly, safely and with more confidence with the electrical tips and techniques used by pros. These electrical tips solve the most common problems you’re likely to encounter.

Overview: Solving unanticipated electrical problems

Replacing a light
fixture is one of
those DIY jobs
that’s theoretically
quick and simple, but
often becomes a three-hour
series of problems.

So we talked with two of
our master electricians.
They’ve seen—and
solved—all of those
frustrations and offered
these tips to help DIYers
through the job quicker
and safer. We won’t show you here, but this article
will walk you through step-by-step on How to Hang a Ceiling Light Fixture.

Flipping the breaker isn't enough

Noncontact voltage detector

You don't have to actually touch a bare wire to check for voltage with this detector. Holding the tip on or close to the wire's insulation is enough.

Even after you turn off the breaker
that controls the light’s circuit, you
can still get shocked. How? Some
junction boxes contain wiring from
multiple circuits. So even if you cut
the power to the light fixture, there
may still be live wires in the junction
box. To be safe, check all the
wires in the box with a noncontact
voltage detector before you disconnect
any wires. Just touch each
wire’s insulation with the
tester. If the light glows,
the wire is live.

Buy extra hardware

Extra mounting brackets

Buy various types of mounting brackets in advance in case the one supplied with the fixture doesn't work.

The mounting brackets supplied
with your fixture may not work with
your junction box. So when you buy
your new fixture, also pick up a few
other styles of mounting brackets. Better to
spend an extra five bucks than to make a trip to
the hardware store in the middle of the job.

Slick solution for long screws

Wire stripper/bolt cutter

Shorten long screws without ruining the threads with a special bolt cutter, which is often a feature on a wire stripper.

If the fixture mounting screws are too long to fit in the
box, you'll need to cut them. A hacksaw works but
makes a mess of the threads. A wire stripper
with built-in bolt cutters is the way to go.
Just thread the screw into the correct
size threaded hole until you get the
length you need and squeeze the
handle. As you remove the screw,
the tool cleans up the threads
at the cut end. Get one at a
home center for about $10.

Short wires, no problem

Extend short wires

Extend short wires with extra wire connected with stab-in connectors of the proper size.

When the wires in the box are too short,
making connections is aggravating. You’ll
want to hunt down whoever installed them
and throttle that person. But instead, just go to
a home center and pick up a few stab-in connectors.
In tight spaces, they’re much easier to
use than twist-on nuts. Push a “pigtail” (a new
piece of wire) into the connector, then push
the connector onto the old wire. Presto! You’ve
got plenty of length to connect to the fixture’s
wires. Make sure the wire you use for the pigtail
is the same gauge as the existing wire.

Aluminum Wiring Caution

If you have aluminum wiring, don’t
work on it yourself. The connections require special
techniques. Call in a licensed pro who’s certified
to work with it. For more information, go to
http://www.cpsc.gov/cpscpub/pubs/516.pdf

Extend the box

Box extender

Add a box extender when the old box is behind the wall surface more than 1/4-in.

If the junction box is
recessed more than 1/4 in.
from the surface of the
wall or ceiling, you’ve got
a code violation. This is
common when a layer of
drywall or wood was
installed over the original
ceiling. To correct it, add a
box extender (about $2). If you
don’t find one for round or
octagonal boxes at home
centers, search online.

Use a third hand

Improvise an extra hand

Bend a scrap of wire to support the fixture while you wire it.

Connecting a fixture takes three hands: one
to hold the fixture and two to make the connections.
If you don’t have a third hand, hang
the fixture from a scrap of wire or a coat
hanger while you make the connections.

Probe for the screw hole

Aligning a screw hole

Align the screw hole with a thin screwdriver.

Many fixtures have a canopy that's
held in place by two screws.
Aligning the first screw is easy
enough because you can tilt the
canopy a little and aim for the
screw hole above it. To align the
second screw, stick a skinny screwdriver
or a nail into the canopy hole
and rotate the canopy until you find
the screw hole.

Check your home wiring before you buy the fixture

If your home was built before 1985, beware: Many new
light fixtures can’t be connected to pre-1985 wiring
because the insulation on the wiring can’t withstand the
heat generated by the fixture. These fixtures carry a warning
on the label: “Use wire rated for at least 90 degrees C.”
If you know your wiring was installed before 1985, you’ll
have to choose a fixture that doesn’t carry this warning.
Hanging fixtures, for example, usually don’t require newer
wiring because they don’t heat the wiring as much as fixtures
that mount directly against the ceiling. The alternative
is to replace the wiring, which may be a small job, or
huge, depending on the situation.

If you don’t know the age of your wiring, look at the fine
print. If you have plastic sheathed cable (Romex is one
common brand) and can see the outer sheathing, look for
“NM-B” or “UF-B.” Or look for “THHN” or “THWN-2” on the
insulation of individual wires. If you see any of these, the
wiring can handle the heat.

Buy better connectors

Wire connectors

Buy connectors with internal metal threads for more secure connections.

The twist-on connectors supplied with
most fixtures are all plastic; no metal
threads inside. They just don’t grip the
wires for an easy, secure connection. So spend an extra few
bucks on a pack of assorted small connectors with metal
threads when you buy the fixture.

Make a strong connection

Connecting stranded wire to solid wire

Extend the stranded wire further into the connector than the solid wire for a solid connection.

Light fixtures almost always require a
connection between solid wire and
stranded. That’s frustrating because
the connector twists and pushes the
stranded wire but doesn’t grab it.
Here’s the solution: First, cut off the
old exposed solid wire and then strip
off 1/2 in. of the insulation. On the
stranded wire, strip off 5/8 in. Hold the
wires together so the stranded wire
extends about 1/8 in. beyond the solid
wire and twist on the connector. The
end of the stranded wire will bunch up
inside the tip of the connector, locked
in place for a secure connection.

Why work in the dark?

Camping headlamp

Carry your flashlight on your head so you don’t have to fumble around in the dark.

If the light fixture and outlets in the room are on different circuits,
plug in a couple of lamps before you shut off the power to the fixture.
Otherwise, strap on a camping headlamp. You’ll find them
everywhere, some for less than $10.

Stripped hole fix

Tapping a stripped hole

An electrician's tap cuts new threads so you don't have to replace the box. You'll need a bigger screw.

The built-in screw holes on a
metal box are easy to strip.
And if that happens, your first
impulse might be to use a
drywall screw. Bad idea—the
sharp tip can poke through
wire insulation. Instead, use
an electrician’s tap (about $9) to
cut new threads in the hole.
That will enlarge the hole
from a No. 8-32 screw size to
a No. 10-32, so you may need
a couple of new screws, too.

Check for ground

Checking for ground

Touch a circuit tester to the ground wire and the hot wire to test the ground. If it lights, the ground is good.

Your new light fixture will have a ground wire (green coated
or bare copper). But if you have an older metal box, there
may not be a ground wire inside the box to connect to.
Adding a ground wire to the box isn’t difficult; just connect
a 6-in. section of bare copper wire to the box by driving a No.
10-32 ground screw (available at home centers) into a
threaded hole in the box. But before you do that, you have to
make sure the box itself is grounded.

Here’s how: turn the power on and make sure the light
switch is turned on. Find the hot wire (typically black or red)
using your noncontact voltage tester. Next, you’ll need a circuit
tester (about $4 at home centers). Touch one of the tester’s
probes to the bare end of the hot wire and the other to the
box. If the light glows, the box is grounded. If not, a ground
wire will need to be run to the box to meet electrical code.
That’s a job for a licensed electrician, unless you’re a very
knowledgeable DIYer.

Chandelier chain too long? There's a tool for that!

Chain pliers

This special tool neatly opens and closes decorative chains.

Raising a chandelier is as easy as removing a
few chain links. But opening and closing
links without scratching or misshaping
them can be a pain. That’s why some
whiz kid invented chain pliers. This
tool bends links open and closed
gently and neatly. Search
online for “Westinghouse
70099” (about $20). Sure, it’s a
splurge, but don’t you
want a tool none of
your buddies have
ever seen?